1. Field of the Invention
The present invention generally relates to surface treating methods and apparatuses, and more particularly to a surface treating method a surface treating apparatus which are suited for treating a substrate surface of a magnetic recording medium and the like.
2. Description of the Related Art
In magnetic recording media such as magnetic disks, a spacing between a head and the magnetic recording medium, that is, a floating amount of the head from the magnetic recording medium, needs to be small in order to achieve a high recording density. The floating amount of the head can be reduced by reducing a substrate surface roughness of the magnetic recording medium.
Conventionally, the substrate surface of the magnetic disk is subjected to a texturing process which carries out a texturing in a circumferential direction of the substrate or, to a polishing process which smoothens and polishes the substrate surface. However, the texturing process and the polishing process cannot avoid damage or the so-called scratches to the substrate surface caused by mixing of foreign particles into a polishing liquid. The generation of scratches is a big obstacle to realizing a high-density recording.
FIGS. 1A and 1B are diagrams for explaining an example of a conventional surface treating method. FIG. 1A is a front view showing a part of a surface treating apparatus, and FIG. 1B is a side view showing a part of the surface treating apparatus. A driving unit (not shown) feeds a polishing tape 1 in a tape feeding direction A via a robber roller 2. A polishing liquid (or slurry) 5 is supplied from a drop-feed nozzle 4, between the tape 1 and a disk substrate 3. The disk substrate 3 is rotated in a direction B as the tape 1 is fed in the tape feeding direction A in a state where the disk substrate 3 makes contact with the tape 1. As a result, the surface of the disk substrate 3 is polished.
Foreign particles may be mixed into the polishing liquid 5 itself or, foreign particles may mix into the polishing liquid 5 when the polishing liquid 5 is supplied from the drop-feed nozzle 4 between the tape 1 and the disk substrate 3 depending on an external environment. In such cases, the foreign particles form scratches on the surface of the disk surface 3 when the tape 1 polishes the surface of the disk substrate 3, and prevent the surface roughness from being further reduced. In addition, a reproduced output obtained from portions formed with the scratches is low compared to that obtained from normal portions on the disk surface 3, and the portions formed with the scratches become defective portions. The problem described above is also encountered when a polishing member other than the tape 1, such as a pad, is used.
For example, disk cleaning apparatuses are proposed in Japanese Laid-Open Patent Applications No. 2007-105624, No. 2000-108022 and No. 11-354480.
If the foreign particles are mixed into the polishing liquid itself or, the foreign particles mix into the polishing liquid when the polishing liquid is being supplied, it is difficult to reduce the surface roughness of the substrate in the case of the conventional surface treating method because the scratches are formed on the substrate surface when the substrate surface is polished.